Second-order difference-frequency wave loads on a floating body in uniform current in the frequency domain

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Second-order difference-frequency wave loads on a floating body in uniform current in the frequency domain

Bakti, Farid P. / Kim, MooHyun

In this study, a formulation for the second-order difference-frequency wave load in the presence of steady uniform current (or forward speed) is presented, and a practical approximate approach is proposed. A potential flow-based solution is formulated to include terms up to the second-order in wave slope and first-order in current speed. In the uniform-flow approximation, the body disturbed and ship-generated steady flows are neglected, assuming slender bodies and low uniform flow speed. The free-surface integral is not included in evaluating the difference-frequency force quadratic transfer function (QTF) considering its relatively unimportant contribution compared to other terms, which significantly reduces the cost of the computational implementation. The present numerical results compare well against published experimental and numerical result. The importance of directly calculating off-diagonal terms of the QTF in the presence of uniform flow is investigated by comparing the present model with other existing approximation methods and with cases without uniform flow.